The conventional substrate storage container such as Front Opening Unified Pod (FOUP) includes, as partly shown in FIGS. 23 and 24, a container main body 1 for accommodating a plurality of semiconductor wafers W in alignment and a door unit that is attachably and removably fitted to an open front 2 of the container main body 1. The container main body 1 is equipped with a plurality of air feed valves and air release valves which enable replacement of air inside the container main body 1 with a purge gas for semiconductor wafers W to protect semiconductor wafers W.
The container main body 1 is formed to have a front open box configuration having an open front 2, and is mounted in position with a load port 81 equipped with a purging device. The door unit is fitted to and removed from the open front 2 by this load port 81. Arranged and fitted at both sides in the rear part of a bottom plate 6 of the container main body 1 are air feed valves for supplying a purge gas for semiconductor wafers W (see the arrows in FIGS. 23 and 24) from the outside to the inside of the container main body 1. Air release valves that exhaust air from the interior to the exterior of the container main body 1 when the purge gas for semiconductor wafers W are supplied are arranged and fitted at both sides in the front part of the bottom plate 6 (see Patent Document 1).
As the purge gas for semiconductor wafers W, inert gases (nitrogen gas etc.) for inhibiting deterioration of the surface conditions of semiconductor wafers W and corrosion of wires, and dry gas can be mentioned, for example. Each air feed valve is optionally connected to a hollow tower nozzle 70 when the air is required to be efficiently replaced with purge gas. This tower nozzle 70 is given as, for example a vertically extended elongate hollow cylindrical form, fixed to the bottom plate 6 of the container main body 1 to communicate with the air feed valve, and has a plurality of blow holes 71 for blowing out purge gas toward the front 2 of the container main body 1, perforated in rows vertically on the peripheral wall thereof (see Patent Document 2).
In a typical substrate storage container, the air is replaced by purge gas in a condition where the container main body 1 is confined when the front 2 of the container main body 1 is fitted with a door unit. Recently, however, replacement with purge gas has come to be performed during processing semiconductor wafers W by processing equipment so as to prevent degeneration of the surface conditions of semiconductor wafers W. In this case, the substrate storage container is mounted on a module called EFEM (Equipment Front End Module) 80, and the door unit is removed from the front 2 of the container main body 1, then the air is replaced with purge gas in the state where the front 2 of the container main body 1 is open (see Patent Document 3).
The EFEM 80 is a transport system that is constructed of a loadport 81, wafer transport mechanism and wafer transport chamber, to perform a semiconductor manufacturing process up to supplying semiconductor wafers W loaded from the load port 81 to the production equipment. Arranged in the ceiling of this EFEM 80 is a fan filter unit (FFU) 82, which blows a large quantity of clean air down toward the floor as indicated by the arrows.
In the above configuration, when the relative humidity inside the container main body 1 of the substrate storage container is desired to be uniformly lowered to a certain level or below by replacement of air with purge gas using the EFEM 80, the container main body 1 of the substrate storage container is set on the load port 81 of EFEM 80, the door unit is removed from the front 2 of the container main body 1, then purge gas is supplied at high pressure from the outside to the inside of the container main body 1 while a large quantity of clean air is blown downwards to the floor from the fan filter unit 82 at the ceiling of EFEM 80.
As a result, the purge gas flows into the tower nozzle 70 through the air feed valves of the container main body 1 and blows out from a plurality of blow holes 71 of the tower nozzle 70 toward the open front 2 of the container main body 1 while flowing from the rear to the front passing through between and in contact with a plurality of semiconductor wafers W. Thus, the air inside the container main body 1 is discharged from the front 2 of the container main body 1 to the outside by the air flow to thereby reduce the relative humidity inside the container main body 1.